Exam Buffer

Why exam buffer exists

Quantivly computes exam duration from imaging data: specifically, from the timestamp of the first slice of the first image to the last slice of the last image. This captures the pure scan time accurately, but it misses everything that happens around the scan itself.

In practice, each exam slot involves more than image acquisition. Staff need time to:

• Escort the patient into the room and get them positioned on the table

• Confirm protocols, place IV lines, or administer contrast or sedation

• Complete post-scan tasks: helping the patient off the table, cleaning and resetting the room, and preparing for the next case

This surrounding time is called patient turnover, and ignoring it leads to an overly optimistic view of scanner utilization and throughput capacity.

Exam buffer solves this by adding configurable pre- and post-exam time windows around each scan, giving a more realistic picture of how long a scanner is truly occupied per case.

Two modes: Fixed buffer and Variable buffer

Fixed buffer

Fixed buffer applies a single, uniform value symmetrically around every exam. For example, a 5-minute fixed buffer adds 5 minutes before and 5 minutes after every scan, for a total of 10 minutes per exam.

The following fixed buffer options are available in visualizations:

• No buffer

• 5 min pre + post

• 7.5 min pre + post

Fixed buffer is a good starting point, but it treats a routine outpatient brain MRI the same as a sedated pediatric case — which is rarely accurate.

Variable buffer

Variable buffer allows you to define rules so that buffer time is automatically adjusted based on the specific characteristics of each exam and patient.

The logic: base buffer + add-ons

Variable buffer is calculated as:

Total buffer = Base buffer + sum of all applicable add-ons

• Base buffer is a symmetrical value (e.g., 5 minutes) added to every exam regardless of any other conditions.
  It can be set to 0 if you want purely rule-driven buffer.

• Add-ons are additional buffer increments layered on top of the base whenever a specific condition is met.
  Multiple add-ons can apply to the same exam — they stack.

Available parameters

Why these parameters matter in practice

• Inpatients typically require more time than outpatients: they arrive by stretcher or wheelchair, may need additional assistance, and often have more complex medical histories that require extra coordination with clinical staff.

• Sedated cases require time before the scan to administer and wait for sedation to take effect, and time after for recovery monitoring.

• Contrast exams require IV placement and a waiting period before imaging can begin, plus time after for monitoring or line removal.

• Pediatric patients (especially infants) require extra handling care, positioning time, and often parental coordination.

  .

Configuration

Variable buffer is configured using JSON in Settings > Buffer Settings.

You can also reach it from the Calendar via Display Settings > Buffer > Manage variable buffer rules.

Permissions

• Admin access is required to edit Buffer Time settings.

• Users without Admin access can still view the settings and use the preview tool.

• The settings apply site-wide, meaning the same variable buffer rules are applied to all users.

How to configure variable buffer settings

JSON syntax

Variable buffer settings are defined using JSON. The configuration follows this structure:

{
  "base_buffer": 5,
  "variable_buffer_rules": {
    "age": [
      {"from_month": 0, "to_month": 6, "buffer": 8},
      {"from_month": 6, "to_month": 24, "buffer": 5}
    ],
    "patient_class": {
      "INPATIENT": 5,
      "OUTPATIENT": 1
    },
    "contrast": {
      "pre_buffer": 15,
      "post_buffer": 5
    },
    "sedated": {
      "pre_buffer": 15,
      "post_buffer": 5
    }
  }
}

Any parameter you don't need can simply be removed from the JSON. For example, to disable contrast-based buffering, delete the "contrast" block entirely.

The ‘Save’ button will only be enabled if the JSON is valid. Make sure to refer to the Parameters section for validation details

Validation rules

Previewing results

A preview tool is available on the right side of the Buffer Settings screen. Enter patient characteristics to simulate what the pre/post buffer would be for a given case before saving your configuration.

Configuration examples

Example 1: Extra time for inpatients and sedated cases

This configuration uses:

• ✅ Base buffer: 6 minutes before and after the exam

• ✅ Sedation rule: 15 minutes before and 5 minutes after the exam

• ✅ Patient class rule: INPATIENT — 5 minutes before and after the exam

This configuration does not use:

• ❌ Contrast

• ❌ Age-based rules

{
  "base_buffer": 6,
  "variable_buffer_rules": {
    "sedated": {
      "pre_buffer": 15,
      "post_buffer": 5
    },
    "patient_class": {
      "INPATIENT": 5
    }
  }
}

This produces four distinct total buffer values, illustrated below:

Example 2: Extra time for young pediatric patients

This configuration uses:

• ✅ Base buffer: 7.5 minutes before and after the exam

• ✅ Age-based rules:

  • One rule for patients between 0 and 12 months

  • Another rule for patients between 12 and 24 months

This configuration does not use:

• ❌ Contrast

• ❌ Sedation

• ❌ Patient class

{
  "base_buffer": 7.5,
  "variable_buffer_rules": {
    "age": [
      { "from_month": 0, "to_month": 12, "buffer": 8 },
      { "from_month": 12, "to_month": 24, "buffer": 5 }
    ]
  }
}

It will effectively create 3 distinct cases, illustrated below:

Example 3 : Contrast-only, no base buffer

This configuration uses:

• ✅ Base buffer: set to 0 minutes

• ✅ Contrast: 10 minutes before and 4 minutes after the exam

This configuration does not use:

• ❌ Age-based rules

• ❌ Sedation

• ❌ Patient class

{
  "base_buffer": 0,
  "variable_buffer_rules": {
    "contrast": {
      "pre_buffer": 10,
      "post_buffer": 4
    }
  }
}

The settings above will result in a using at 14 mn buffer for contrast exams, and a 0 mn buffer for all other exams.

Finding out the patient classes

If you need to access the list of patient classes used at your site, you can run the following query in SQL Pad.

SELECT DISTINCT patient_class
FROM public.appointment

Where the variable buffer is used